Heat exchanger

ABSTRACT

A short, compact heat exchanger is disclosed to include an inner tube, an intermediate tube and an outer tube concentrically arranged together to form a triple-tube structure, a thermal fluid flowing through the intermediate tube, a heat-transfer medium flowing through the outer tube and the inner tube to make heat exchange with the thermal fluid. If the thermal fluid can be a refrigerant and the heat-transfer medium can be room temperature water so that the heat exchanger can be used in an air-conditioning refrigerating system to substitute for a condenser or evaporator.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to heat exchangers and more particularly,to a triple-tube structure type heat exchanger.

2. Description of the Related Art

A heat exchanger is a device built for efficient heat transfer from onemedium to another. Within the equipment, at least two media areseparated by a solid wall for heat transfer, i.e., high temperaturemedium discharges heat energy, and low temperature medium absorbs heatenergy. Heat exchangers are widely used in our daily life, for example,for cold making application or hot application.

Heat exchangers are classified into double-pipe heat exchangers, shelland tube heat exchangers, plate type heat exchangers, . . . and etc.,wherein:

(1) In double-pipe heat exchangers, two tubes are concentricallyarranged together so that two fluids respectively flow through the innerpath surrounded by the inner tube and the outer path surrounded by theouter tube outside the inner tube, and the wall of the inner tubetransfers heat from one fluid to the other. The outer tube is usuallycovered with a layer of heat insulation material to reduce heat loss. Adouble-pipe heat exchanger has the advantages of simple structure, lowcost and ease of maintenance. The significant drawback of a double-pipeheat exchanger is its limited heat transfer surface area.

(2) In shell and tube heat exchangers, a bundle of tubes is set inside ashell (a large pressure vessel). One fluid runs through the tubes, andanother fluid flows over the tubes (through the shell) to transfer heatbetween the two fluids. Shell and tube heat exchangers can be classifiedinto fixed head exchangers, floating head exchangers, and U-tubeexchangers. In a fixed head exchanger, the bundle of tubes has the bothends affixed to flanges of the shell by screw bolts. A fixed headexchanger has the advantages of simple structure and low cost, howeverthe connectors of the tubes of a fixed head exchanger may break to causeleakage when the tubes expand due to heat. In a floating head exchanger,the bundle of tubes has one end affixed to a flange of the shell and theother end fastened to a float floatable relative to the shell. Afloating head exchanger eliminates tube connector leakage; however ithas a complicated structure and high manufacturing cost. In a U-tubeexchanger, the tubes are bent in the shape of a U, and the ends of eachtube are connected to plenums through holes in tubesheets. A U-tubeexchanger has the advantages of simple structure and low manufacturingcost and allows the bundle of tubes to curve when expands due to heat,however, due to the drawback of cleaning difficulty, a U-tube exchangeris not suitable for fluids that are easy to scale the tubes.

(3) In plate type heat exchangers, multiple, thin, slightly-separatedplates that have very large surface areas and fluid flow passages forheat transfer are fastened together in a stacked-plate arrangement.Stainless steel plates are commonly used in plate type heat exchangers.Some plates may be stamped with “chevron” or other patterns, whereothers may have machined fins and/or grooves to enhance heat transfereffect. Plate type heat exchangers have the advantages of smalldimension, light weight, ease of maintenance and plate numberadjustability, and high fluid disturbance in heat exchanger. However,due to a great sealing peripheral area, a plate type heat exchangertends to cause leakage. Further, a plate type heat exchanger has lowprocessing capacity and low heat and pressure resisting power. Theworking temperature of a plate type heat exchanger must be controlledbelow 150° C. When the plates are covered with a coat of hard substance,the plate type heat exchanger must be dismounted for cleaning.

Accordingly, it has been determined that there is a continuous need forheat exchangers that overcome, alleviate, and/or mitigate one or more ofthe aforementioned and other deleterious effects of the prior art heatexchangers.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances inview. It is one object of the present invention to provide a heatexchanger, which utilizes a triple-tube structure type and effectivelytransfers the surface and core energy of a hot or cold thermal fluid,for example, refrigerant with oil through a heat-transfer medium, forexample, water, achieving an excellent heat exchange effect. It isanother object of the present invention to provide a heat exchanger,which not only effectively increases the conducting heat area tocorrespond with the speed and capacity of the flow and increases theefficiency of heat exchanging and has simple structure and low costcharacteristics.

To achieve these and other objects of the present invention, a heatexchanger comprises an inner tube, an intermediate tube and an outertube concentrically arranged together to form a triple-tube structure, athermal fluid flowing through the intermediate tube, and a heat-transfermedium flowing through the outer tube and the inner tube, enabling thesurface energy and core energy of the thermal fluid to be transferredthrough the peripheral wall of the intermediate tube and the peripheralwall of the inner tube to make heat exchange with the heat-transfermedium that travels

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of a heat exchanger in accordance with thepresent invention.

FIG. 2 is sectional view of the heat exchanger in accordance with thepresent invention.

FIG. 3 is a schematic drawing showing an application example of thepresent invention in an air-conditioning refrigerating system

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 and 2, a heat exchanger in accordance with thepresent invention comprises an inner tube 11, an intermediate tube 12,and an outer tube 13. The inner tube 11, the intermediate tube 12 andthe outer tube 13 are metal tubular members made from a metal materialhaving a high coefficient of thermal conductivity, preferably, copper.The outer tube 13 surrounds the intermediate tube 12, which surroundsthe inner tube 11, i.e., the inner tube 11, the intermediate tube 12 andthe outer tube 13 are concentrically mounted together to form a tripletube structure. For heat exchange, a thermal fluid 2, for example,refrigerant with lubricating oil is filled to travel through theintermediate tube 12 in one direction, and a heat-transfer medium 3, forexample, room temperature water is filled to travel through the outertube 13 and the inner tube 11 in a direction reversed to the flowingdirection of the thermal fluid 2.

Referring to FIG. 2 again, the surface energy and core energy of thethermal fluid 2 are transferred through the peripheral wall of theintermediate tube 12 and the peripheral wall of the inner tube 11 tomake heat exchange with the heat-transfer medium 3 that travels throughthe outer tube 13 and the inner tube 11 in a direction reversed to theflowing direction of the thermal fluid 2. Therefore, the length anddimension of the heat exchanger can be greatly reduced while achievingthe expected heat exchange performance. As stated above, the thermalfluid 2 can be a refrigerant, such as high-temperature gaseousrefrigerant or low-temperature fluid refrigerant, and the heat-transfermedium 3 can be room temperature water. By means of heat transferfunctioning of the triple tube structure of the heat exchanger, the heatexchanger has the functions of a condenser and an evaporator. However,it is to be understood that the thermal fluid 2 and the heat-transfermedium 3 are not limited to the aforesaid refrigerant and water.Alternatively, the thermal fluid 2 can be any of a variety of other coldor hot fluids or gasses, and the heat-transfer medium 3 can be any of avariety of other hot or cold fluids or gasses. Therefore, the heatexchanger of the present invention can be used in an air-conditioningrefrigerating system as well as any other industry, such as chemicalindustry, petroleum industry, dynamic industry or nuclear energyindustry.

FIG. 3 illustrates an application example of the present invention in anair-conditioning refrigerating system. As illustrated, theair-conditioning refrigerating system comprises a compressor 4, adelivery line 5, a first heat exchanger 6, a reinforcing condensationdevice 7, an expansion device 8, and a second heat exchanger 9.

The compressor 4 uses a motor to suck in (recycle) a thermal fluid 2from the delivery line 5, such as, low-pressure low-temperature gaseousrefrigerant, for example, RS-22 with lubricating oil (hereinafter calledas oil) and to compress it into a high-pressure high-temperature, forexample, 500 psi, 168.6° C. gaseous refrigerant with oil, enabling thehigh-pressure high-temperature gaseous refrigerant with oil to bedischarged out of the compressor 4 into the delivery line 5 in direction“a”.

The delivery line 5 has one end connected to the discharge end of thecompressor 4, and the other end connected to a first intermediate tube62 of the first heat exchanger 6.

The first heat exchanger 6 converts the high-pressure high-temperaturegaseous refrigerant into a fluid refrigerant by means of a heat exchangeaction with a heat-transfer medium 3, for example, water. The first heatexchanger 6 further comprises a first inner tube 61 concentricallyinserted through the first intermediate tube 62, and a first outer tube63 concentrically surrounds the first intermediate tube 62. For enablingthe first heat exchanger 6 to work as a condenser, a linking manifold isrespectively connected to the upstream and downstream ends of the firstintermediated tube 62 to deliver the refrigerant, a three-way shunt tube64 is connected to the downstream ends of the first inner tube 61 andthe first outer tube 63 to guide the heat-transfer medium 3, forexample, 28.4° C. room temperature water into the first inner tube 61and the first outer tube 63 in direction “b1”, enabling theheat-transfer medium 3 to flow through the first inner tube 61 and firstouter tube 63 toward the upstream end of the first heat exchanger 6 andto perform a heat exchange process with a high-temperature, for example,140.5° C. refrigerant with oil that flows through the first intermediatetube 62 from the downstream toward the upstream, so that the three-waygather tube 65 that is connected to the upstream ends of the first innertube 61 and the first outer tube 63 discharges the gathered two flows ofhot water in direction “b2”. According to test, the temperature of thedischarged hot water is as high as 75.3° C. After condensed through thefirst heat exchanger 6, the liquid refrigerant with oil flows throughthe downstream end of the first intermediate tube 62 into the deliveryline 5.

Therefore, by means of the heat exchange process between the thermalfluid 2 and the heat-transfer medium 3 through the first heat exchanger6, the temperature of the refrigerant with oil is effectively loweredand then delivered by the delivery line 5 to the reinforcingcondensation device 7.

The reinforcing condensation device 7 is formed of a plurality ofcapillary tubes 71. These capillary tubes 71 guide in the liquidrefrigerant with oil and bubbles from the first heat exchanger 6 andfunction as a condensing efficiency enhancement device like TaiwanPatent Publication Number 494222 that is issued to the present inventor,thereby regulating flowing of liquid, air and oil. Therefore, when theliquid refrigerant with oil flows through the capillary tubes 71 of thereinforcing condensation device 7, bubbles are stopped outside thecapillary tubes 71, enhancing the condensing efficiency. After passedthrough the capillary tubes 71, the liquid refrigerant with oil isgathered together again and guided into the delivery line 5 at thedownstream so that the temperature of the liquid refrigerant with oil islowered to 33° C. after a secondary condensing process.

The expansion device 8 can be, for example, an expansion valve or asingle capillary tube, adapted to force the liquid refrigerant passingtherethrough into a mist, lowering the pressure of the liquidrefrigerant to, for example, about 50 psi for evaporation by theposterior second heat exchanger 9, enabling the mist of refrigerant tobe evaporated under a low pressure and low temperature status.

The second heat exchanger 9 guides the aforesaid mist of refrigerantdischarged by the expansion device 8 into the second intermediate tube92 and toward the maniford of the downstream. Similar to the aforesaidfirst heat exchanger 6, the second heat exchanger 9 comprises a secondinner tube 91, a second intermediate tube 92 surrounds the second innertube 91 concentrically, and a second outer tube 93 surrounds the secondintermediate tube 92 concentrically. For enabling the second exchanger 9to work as an evaporator, a three-way shunt tube 94 is connected to thedownstream ends of the second inner tube 91 and the second outer tube 93to guide the heat-transfer medium 3, for example, 28.4° C. roomtemperature water into the second inner tube 91 and the second outertube 93 in direction “c1”, enabling the 28.4° C. room temperature waterto perform a heat exchange process with the high-temperature refrigerantwith oil that flows through the second intermediate tube 92 from theupstream toward the downstream, so that the mist of refrigerant isevaporated into a gaseous refrigerant. At this time, the three-waygather tube 95 that is connected to the downstream ends of the secondinner tube 91 and the second outer tube 93 discharges the gathered twoflows of icy water in direction “c2”. According to test, the temperatureof the discharged icy water is as low as 17.4° C. After evaporationthrough the second heat exchanger 9, the gaseous refrigerant with oilflows through the downstream end of the second intermediate tube 92 intothe delivery line 5, which has its other end connected to the intake endof the compressor 4 for enabling the gaseous refrigerant to be furthercompressed and discharged by the compressor 4. The icy water isdelivered to the cooling coil at each air outlet so that the coolingcoil at each air outlet absorbs heat energy from surrounding air,enabling low temperature air to flow out of each air outlet into theinside of the house to lower the temperature in the house. Thus, an airconditioning circulation system is established.

The aforesaid second heat exchanger 9 converts the refrigerant from amist (liquid state) into a gaseous state, enabling the refrigerant withoil to absorb heat and to have its temperature be raised to 11.1° C.Further, as shown in FIG. 3, the refrigerant with oil and the water flowthrough the first heat exchanger 6 and the second heat exchanger 9 inthe reversed directions. Further, to avoid loss of heat energy, thefirst heat exchanger 6 and the second heat exchanger 9 are respectivelywrapped with an insulation material, for example, insulation polymercompound.

Further, to make sure that the temperature of the gaseous refrigerantreaches 168.6° C. at the time when it is discharged, the two segments ofthe delivery line 5 that are respectively connected to the intake endand discharge end of the compressor 4 are attached together and wrappedwith an insulation material for making a heat exchange process so thatthe temperature of the gaseous refrigerant with oil can be raised toabout 30.9° C. before returning to the compressor 4. By means of raisingthe temperature of the gaseous refrigerant with oil before returning tothe compressor 4, the oil is softened, facilitating smooth running ofthe compressor 4. Because the discharge capacity is enhanced, heat iseffectively released from the coil of the compressor 4 to increase thetemperature of the discharged gaseous refrigerant, thereby raising thecompression ratio and lowering the ampere level.

Therefore, the application of the invention has the advantage ofutilizing triple-tube structure type heat exchangers to effectivelytransfer the surface and core energy of a hot or cold thermal fluidthrough a heat-transfer medium. A heat exchanger in accordance with thepresent invention effectively increases heat transfer surface area toenhance heat exchange performance and has simple structure and low costcharacteristics. Further, a triple-tube structure type heat exchangerconstructed in accordance with the present invention can be used as acondenser or evaporator in a heat-exchange circulation system, enablingthe heat-exchange circulation system to provide hot/icy water, avoidingwaste of heat energy and reducing discharge of waste heat.

Although a particular embodiment of the invention has been described indetail for purposes of illustration, various modifications andenhancements may be made without departing from the spirit and scope ofthe invention. Accordingly, the invention is not to be limited except asby the appended claims.

1. A heat exchanger, comprising: a triple-tube structure, said triple-tube structure comprising an inner tube, an intermediate tube concentrically surrounding said inner tube, and an outer tube concentrically surrounding said intermediate tube, said inner tube and said intermediate tube and said outer tube having different diameters; a thermal fluid flowing through said intermediate tube; and a heat-transfer medium flowing through said outer tube and said inner tube; and wherein the surface energy and core energy of said thermal fluid are respectively transferred to said heat-transfer medium through said intermediate tube and said outer tube.
 2. The heat exchanger as claimed in claim 1, wherein the flowing direction of said thermal fluid in said intermediate tube is reversed to the flowing direction of said heat-transfer medium in said outer tube and said inner tube.
 3. The heat exchanger as claimed in claim 1, wherein said inner tube and said outer tube have a three-way pipe respectively connected to the upstream and downstream ends thereof to delivery the heat-transfer medium; said intermediate tube has a linking manifold respectively connected to upstream and downstream ends thereof to delivery said heat-transfer medium.
 4. The heat exchanger as claimed in claim 1, wherein said thermal fluid is a cold or hot liquid or gas; said heat-transfer medium is a hot or cold liquid or gas.
 5. The heat exchanger as claimed in claim 4, wherein said thermal fluid is a refrigerant and lubrication oil; said heat-transfer medium is room temperature water.
 6. The heat exchanger as claimed in claim 1, further comprising an insulation material wrapped about said triple-tube structure.
 7. The heat exchanger as claimed in claim 1, wherein said inner tube, said intermediate tube and said outer tube are made of a metal material.
 8. The heat exchanger as claimed in claim 1, wherein said metal material is copper. 